This invention relates to apparatus and methods for working on flexible sheet material such as fabric webs from which garments or upholstery are made, and deals more particularly with apparatus and methods for supporting such sheet material in a spread condition and for cutting or otherwise working on such sheet material while so supported.
In the past it has been well known to cut fabric and other sheet material by spreading it either as a single layer or as a layup of a number of layers over a supporting surface and to then cut the single layer or layup to produce pattern pieces by moving a cutter either by hand or automatic control along desired lines of cut. It is also well known to make such supporting surface penetrable by the cutting tool of the cutter so that in the cutting process the tool may not only pass completely through the material being cut but may also extend some distance downwardly beyond the supporting surface and into the bed of material providing such surface.
The use of bristles to form a penetrable supporting surface in a cloth cutting machine is known in the art and is shown for example in U.S. Pat. Nos. 2,445,150; 3,548,697; 3,776,072; 3,942,781; 4,205,835; and 4,391,170. The general aim of the prior art bristle beds as exemplified by most of these patents has been to provide a substantially continuous supporting surface for the sheet material to be cut so that the support surface acts as an anvil in conjunction with the cutting tool. That is, the desire has been to provide a supporting surface which rigidly backs up the sheet material supported thereon to prevent the material from moving downwardly when a downward pressure is applied to the material as by a reciprocating cutting tool, while nevertheless allowing a sharp cutting edge of a cutting tool to pass downwardly beyond the supporting surface into the space occupied by the bristles. This anvil type supporting surface has been obtained in part by using bristles with flat or blunt surfaces at their upper ends.
Bristle beds of the known type providing anvil-like supporting surfaces have the disadvantage that material spread on such supporting surface tends to be easily displaced in the plane of the supporting surface when subjected to a force appearing in that plane as for example the force exerted thereon by a forwardly facing cutting edge of a cutting tool, or by the undersurface of a presser foot, moved forwardly along a line of cut relative to the material during a cutting procedure. This tendency of the material to move or shift in the plane of the supporting surface causes cutting errors and is due both to a tendency of the material to slip relative to the ends of the bristles and also due to the tendency of the bristles to bend, the bristles usually being relatively long and thin and therefore quite flexible.
The general aim of the invention is therefore to provide a bristle bed providing a supporting surface for holding sheet material in a cloth cutting machine or the like which bristle bed cooperates with the material spread thereon to inhibit its movement in the plane of the supporting surface. In keeping with this object, further objects of the invention are to inhibit the lateral movement of the material spread on the supporting surface both by reducing or eliminating slippage of the material relative to the bristles and by reducing bending of the bristles.
A further object of the invention is to provide a bristle bed, or a machine using a bristle bed, of the foregoing character wherein the holding effect of the bed with respect to sheet material spread onto it is normalized so as to be substantially the same for different types of materials ranging for example from hard tightly woven ones to soft loosely woven ones.
Another object of the invention is to provide a cloth cutting machine particularly well adapted to the efficient cutting of either a single sheet of material or of a low layup of several sheets of material without the need for covering the single layer or the low layup with a sheet of air-impermeable material which works in conjunction with a vacuum applied to the supporting surface to aid in holding the material in place while it is cut, the machine, however, being useable with such sheet of air-impermeable material combined with a vacuum applied to the supporting surface if desired, which may be of benefit when cutting relatively high layups of material.
Another object of the invention is to provide a bristle bed, or a machine using a bristle bed, wherein when a vacuum is applied to the space containing the bristles the flow of air is so controlled that the vacuum is channelled substantially directly to areas of a sheet of work material spread on the material supporting surface provided by the bed and so that a portion of the associated area of the supporting surface may be left uncovered by work material or by supplemental air impervious sealing sheet material without drastically reducing the degree of vacuum appearing over the remaining portion of the associated area of the supporting surface.
Another object of the invention is to provide a bristle bed of the foregoing character, and a related method, particularly useful with a vacuum applied to the space containing the bristles to aid in holding sheet material to the supporting surface and also particularly useful with positive air pressure applied to the bristle space to aid in removing cut sheet material from the supporting surface.
Another object of the invention is to provide a bristle bed and machine of the foregoing character, and a related method, wherein the bristles of the bristle bed are of such a size and shape and are packed to such a density that the bristle bed offers a substantial resistance to the flow of air therethrough in a plane parallel to the bed so that when a vacuum is applied to only a portion of the bristle bed the degree of vacuum will gradually diminish with distance from the vacuumized portion.
A still further object of the invention is to provide bristle blocks for constructing bristle beds of the foregoing character and which may be made as simple injection molded plastic units.
Many other objects and advantages of the invention will be apparent from the following description of a number of embodiments of the invention taken in conjunction with the accompanying drawings.